T(2n-1,n), array T as in A054134.

Terms

a(0) =2a(1) =6a(2) =31a(3) =180a(4) =1101a(5) =6901a(6) =43828a(7) =280664a(8) =1807909a(9) =11698479a(10) =75973701a(11) =494890116a(12) =3231949644a(13) =21153128028a(14) =138712184488